class A {

  final double PI=3.1415926;// PI是常量

  public double getArea(final double r) {

     return PI*r*r;

  }

  public final void speak() {

     System.out.println("您好，How's everything here ?");

  } 

}

public class Example5_9 {

   public static void main(String args[]) {

      A a=new A();

      System.out.println("面积："+a.getArea(100));

      a.speak();     

   }

}
